Crossed polarizers

9. Contrast methods for Leica DM4000 B/DM4500 P/DM5000 B

9.1.4.2DM4500 P - examinations

in polarized transmitted light

One polarizer only

If specimens need to be examined using other transmitted light methods, such as bright field, phase contrast and dark field, instead of with polarizers, then it is usually sufficient to switch off the analyzer or polarizer. If the brightness of the image is not adequate, the polarizer and the analyzer need to be switched off. Stained, bire- fringent specimens may exhibit brightness or color fluctuations when the specimen stage or the polarizer is rotated (with the analyzer switched off). This is called dichroism or pleo- chroism, which is an important indication when examining crystals.

However, this effect can be simulated by non- polarizing microscopes, because they do not contain depolarized quartz plates, or when an incident light reflector is left in the beam path during the transmitted light method. This also applies to using the 1.6x tube lens in the DM4500 P.

Fig. 67 Crossing the polarizers for observation using the Bertrand lens, objective with high aperture, without spec- imen

acrossed precisely

bnot crossed precisely

If pressure is present in the condenser or in the objective, position "a" cannot be set at all

According to DIN and ISO ratings the run of the vibration directions corresponds to the table on p. 63. However, when polarizers are crossed, these vibrations have the same polarized optical appearances as they do when each of the polar- izers are interchanged by 90°.

If the specimen contains a large amount of non- birefringent or opaque particles, then the ana- lyzer is usually turned a few degrees away from the cross position to make these particles somewhat visible (for specimens that remain dark when the polarizers are crossed precisely). Examinations are not usually performed when the polarizers are parallel because this configu- ration is not sensitive enough to detect birefrin- gent elements.

Changing the brightness when rotating birefrin- gent objectives

When the specimen stage is rotated, the bright- ness of birefringent (anisotropic) specimens changes periodically. When the specimen is ro- tated, a total of 4 extinction positions (also called normal position) occur at each 90° inter- val. Exactly 45° between 2 extinction positions, 4 orientations of maximum intensity occur, the diagonal or 45° positions. In extinction, the specimen vibration directions are parallel to the transmission directions of the polarizers; at maximum intensity, the specimen vibration di- rections represent the bisectors of the polarizer directions. The cross-hairs in the (right) eyepiece on the polarizing microscope can be rotated N – S/E – W; therefore, they can be rotated in the direction of polarization or 45°, or set up according to the specimen vibration directions when in a diagonal position.

DM4500P, DM5000B, DM4000M specifications

The Leica DM4000M and DM4000B are state-of-the-art microscopes designed for professional use in the fields of biology, materials science, and clinical applications. Renowned for their precision and innovative features, these instruments are perfect for researchers and clinicians needing high-resolution imaging capabilities.

One of the standout features of both models is the advanced motorized focusing system, which allows for swift adjustments and precise control. This feature is particularly useful in time-sensitive research environments, where accuracy and speed are paramount. The ergonomically designed focus mechanism promotes user comfort during prolonged observation sessions.

Both the DM4000M and DM4000B incorporate the revolutionary Leica Application Suite (LAS) software. This intuitive platform is designed to maximize the functionality of the microscope, enabling users to capture, analyze, and share images seamlessly. The software’s integrated tools are perfect for documenting findings and enhancing research productivity.

Another notable characteristic of the DM4000 series is the modular design, which allows for easy customization and upgrading. This aspect ensures that users can tailor their microscopes to meet specific research needs, whether it be for fluorescence microscopy, phase contrast, or even special imaging techniques like HSR or IR.

The high-performance optics provide exceptional image contrast and clarity, allowing users to observe minute details in samples. The combination of high numerical aperture objectives and advanced optical coatings enhances the resolution, making the DM4000 series ideal for examining intricate biological specimens as well as materials with complex textures.

The DM4000B model is particularly suited for routine clinical applications, featuring specific tools designed for rapid diagnosis and efficient workflows. Its user-friendly interface and dedicated clinical applications streamline laboratory processes, making it an essential device in any clinical setting.

Additionally, both models are equipped with LED illumination, which offers consistent light intensity and color temperature. This feature improves sample clarity while reducing heat generation, thereby protecting sensitive specimens during prolonged observation periods.

In conclusion, the Leica DM4000M and DM4000B microscopes represent a blend of advanced technology, intuitive design, and high adaptability. Their user-focused features and exceptional optical performance make them indispensable tools for researchers and clinical professionals aiming for excellence in microscopy.

Leica DM4500P, DM5000B, DM4000M manual Crossed polarizers

Models: DM4500P DM5000B DM4000M